The present invention relates to a pressing device and a friction plate for improving response sensitivity of accelerator operation, provided in a system for directly or indirectly driving an engine-output control device, for example, an intake throttle valve, according to a pressed amount of an accelerator.
In a gasoline engine vehicle, opening and closing the intake throttle valve perform the control of the engine output. In a diesel engine vehicle, rotating a plunger of an injection pump performs the control of the engine output.
To perform control of the engine output, a wire cable connects an accelerator pedal to the output control device, for example, the intake throttle valve or the plunger of the injection pump. Thus, the output control device is driven according to a driver""s operation of the accelerator.
In recent years, an actuator method is in practical use to control the output control of the gasoline engine vehicle. In the actuator method, a pressed amount of the accelerator is converted into an electric signal to operate an actuator so that the actuator opens and closes the intake throttle valve (Japanese Utility Model Application Laid-Open No. 59-41708).
In the actuator method, because a wire cable is much shorter than that of the conventional one, the degree of the resistance of the wire cable applied to driver""s foot is small. Thus, the driver has difficulty in operating the accelerator, which may cause the driver to be much fatigued and an accident to occur.
This problem also occurs in the diesel engine vehicle when the system adopts a short wire cable.
To overcome the problem, an apparatus for improving a response sensitivity of the accelerator operation is known (Japanese Patent Application Laid-Open Nos. 9-280076, 9-236030).
In the apparatus disclosed in Japanese Patent Application Laid-Open No. 9-236030, the wire cable connects the rotary shaft for driving the engine-output control device directly or indirectly to the accelerator pedal so that a resistance is applied to the rotary shaft, of the mechanism for driving the output control device, that rotates according to an operated amount of the accelerator. The pressing device in the apparatus has a metal plate for preventing deformation such as flexure and a sheet-shaped friction plate, for example, the friction plate, made of fluorocarbon resin, bonded to the metal plate. The pressing device is constantly elastically pressed against a disk fixed to the rotary shaft by means of a spring member, which allows a driver to perform the operation of the accelerator smoothly.
The friction plate is used to generate a difference between the accelerator pedal-pressing force and the return force of the accelerator. If the difference is small, the accelerator pedal is moved by a slight change of the accelerator pedal-pressing force, although the driver desires a vehicle speed constant by pressing the accelerator pedal to a certain degree. Thus, it is difficult for the driver to operate the accelerator pedal. If the difference is large, it is easy for the driver to operate the accelerator pedal when the driver desires a vehicle speed constant by pressing the accelerator pedal to a certain degree. However, when the driver changes the vehicle speed, the driver feels uncomfortable in the operation of the accelerator pedal. That is, the driver feels that the accelerator pedal is heavy in pressing it, and it is difficult for the driver to return the accelerator pedal to an original position.
However, the above-described pressing device having the plate-shaped member bonded to the sheet-shaped friction plate made of fluorocarbon resin is inferior in the resistance to creep and self-wearability that are required for the pressing device for use in the apparatus for improving response sensitivity of accelerator operation by applying a resistance to accelerator operation.
Consequently, the feeling for the accelerator pedal is varied owing to a fluctuation of a pressing load of the pressing device caused by creep and self-wear. Further, chattering in the rotation of the pressing device and the return function of the accelerator deteriorate.
Another problem of the above-described pressing device is that there is a fear that the plate-shaped member and the sheet-shaped friction plate made of fluorocarbon resin may separate from each other. Still another problem of the above-described pressing device is that a bonding process is essential in the process of producing the pressing device. That is, the pressing device is produced with poor productivity.
The present invention has been made in view of the above-described situation. Thus, it is an object of the present invention to provide a pressing device, for an apparatus for improving response sensitivity of accelerator operation, superior in productivity because of elimination of a bonding process, having an appropriate degree of a frictional force and sliding-contact performance, and having an improved resistance to wear.
It is another object of the present invention to provide a friction plate, for the pressing device, which is made of fluorocarbon resin and used in combination with a plate-shaped member and which has an appropriate degree of a frictional force and sliding-contact performance, and having a greatly improved resistance to wear and creep.
The pressing device of the present invention, for improving response sensitivity of accelerator operation, for imparting a friction resistance to a rotary shaft driving an engine-output control device directly or indirectly to apply a resistance to an operation of an accelerator comprises a molded product made of a resinous material whose flexural strength is 5 MPa or higher and a flexural modulus of elasticity is 3,300 MPa or higher.
The pressing device can be obtained as a mono block molding product by the resinous material having flexural strength of 50 MPa or higher and the flexural modulus of elasticity of 3,300 MPa or higher.
The resinous material is injection-moldable and consists of one of the following resins or a mixture thereof: polyphenylene sulfide resin (hereinafter referred to as PPS), polyimide resin (hereinafter referred to as PI), polyamideimide resin (hereinafter referred to as PAI), polyether imide resin (hereinafter referred to as PEI), polyether ether ketone resin (hereinafter referred to as PEEK), polyether ketone resin (hereinafter referred to as PEK), polyether nitrile resin (hereinafter referred to as PEN), polyamide resin (hereinafter referred to as PA), aromatic polyester resin, and polyacetal resin (hereinafter referred to as POM).
The resinous material is a resinous composition containing a solid lubricant added to the injection-moldable resin. The solid lubricant is powder of tetrafluoroethylene resin. It is possible to improve the resistance of the pressing device that is an monoblock molding product by adding the solid lubricant to the injection-moldable resin.
The other resinous material for the pressing device of the present invention has a flexural strength of 50 MPa or higher and a flexural modulus of elasticity of 3,300 MPa or higher and consists of a molded product of thermosetting resin. The thermosetting resin is aromatic thermosetting resin or phenol resin.
The friction plate of the present invention, for improving response sensitivity of accelerator operation, imparts a friction resistance to a rotary shaft driving an engine-output control device directly or indirectly to apply a resistance to an operation of an accelerator. The friction plate comprises a fluorocarbon resinous composition containing fluorocarbon resin and at least one of a whisker whose Mohs hardness is 5 or less, a carbon fiber, and a hard resinous powder.
The fluorocarbon resin is selected from tetrafluoroethylene (hereinafter referred to as PTFE) and/or modified tetrafluoroethylene (hereinafter referred to as modified PTFE).
Owing to the action of the ingredient such as the whisker, the carbon fiber and/or the hard resinous powder, it is possible to greatly improve the wear and creep resistance of the fluorocarbon resinous composition of the friction plate.